1. Field of the Invention
The present invention is generally related to a cylinder liner for an internal combustion engine and, more particularly, to a cylinder liner for a marine engine that provides an improved degree of insulation between the temperature within the cylinder and the temperature in cooling passages formed in the engine block.
2. Description of the Prior Art
U.S. Pat. No. 4,447,275, which issued to Hiraoka et al. on May 8, 1984, describes a cylinder liner for an internal combustion engine. The liner has a white cast iron layer formed by remelting and cooling a part or whole of areas of the outer peripheral surface of the cylinder liner. A thermally affected layer is also formed between the white cast iron layer and the parent material. This cylinder liner has improved anti-cavitation properties.
U.S. Pat. No. 4,662,321, which issued to Devaux on May 5, 1987, describes a method and apparatus for regulating the temperature of the inside surface of internal combustion engine cylinder liners. The device provides a method of regulating the temperature of the inside surface of cylinder liners in an internal combustion engine which is cooled by a flow of cooling fluid. The method includes the improvement whereby the temperature of the cooling fluid is regulated in such a manner as to maintain the temperature of the inside surface of the cylinder liners at a reference temperature regardless of the engine load.
U.S. Pat. No. 4,903,652, which issued to Field et al. Feb. 27, 1990, describes a cylinder liner insert and method of making an engine block. The method relates to casting-in-place iron cylinder liners in a light alloy, such as aluminum. Engine blocks can be made by using a cylinder liner insert that comprises at least two generally cylindrical cylinder liners which are joined together along aligned portions of the liners.
U.S. Pat. No. 5,115,771, which issued to Ozawa on May 26, 1992, describes a method of cooling cylinder liners in an engine. It includes an apparatus for cooling a plurality of cylinder liners in an engine with a thermal insulating layer comprising an annular groove which is formed in a region in the vicinity of the upper part of each cylinder liner in the cylinder block while surrounding the upper part of the cylinder liner in a slightly spaced relationship relative to the cylinder liner in order to positively elevate the temperature of the wall surface of the cylinder liner at the upper part of the same and moreover a water jacket is formed in the cylinder block so as to allow coolant to flow from the lower part toward the upper part of the cylinder liner.
U.S. Pat. No. 5,165,367, which issued to Morris on Nov. 24, 1992, describes cylinder liners which have a top boss which is an interference fit in the engine block and a mid-stop flange. The outer portion of the liner between the top boss and mid-stop flange forms a wall of a coolant passage. A cylindrical inner portion of the liner is at least 30% of the length of the liner and has a groove in the outer surface thereof adjacent to the bottom end.
U.S. Pat. No. 6,044,820, which issued to Domanchuk et al. on Apr. 4, 2000, describes a method of providing a cylinder bore liner in an internal combustion engine. The method comprises making an engine block with cylinder bores, forming a spray-formed cylinder liner with a predetermined internal diameter and a predetermined external diameter, heating the cylinder block, inserting the cylinder liner in the bore, and permitting the cylinder block to cool such that the liner is locked in position in the bore by compressive forces.
U.S. Pat. No. 6,123,052, which issued to Jahn on Sep. 26, 2000, describes a waffle cast iron cylinder liner. The cylinder liner is intended for use in an engine block. The liner is cast to have a number of longitudinal grooves and machined to have a number of intersecting annular grooves to create an inverted waffle-like pattern of ridges and grooves on the outer circumferential surface of the liner. This pattern significantly increases the surface area through which cooling of the liner occurs and, thus, increases the liners cooling capacity by approximately 30 to 40 percent.
U.S. Pat. No. 6,182,629, which issued to Gobbels et al. on Feb. 6, 2001, describes a method of making a cylinder liner. A cylinder liner for an internal combustion engine includes a tubular wall having circumferentially spaced thickened wall portions.
U.S. Pat. No. 6,220,214, which issued to Kojima et al. on Apr. 24, 2001, describes a cylinder liner formed with cross-hatching grooves. A cylinder liner formed of a cast iron and having an inner peripheral surface subjected to honing is described. The honing forms cross-hatching grooves on the surface.
U.S. Pat. No. 6,675,750, which issued to Wagner on Jan. 13, 2004, describes a cylinder liner. A cooling system of an internal combustion engine has a wet-sleeve cylinder liner that improves heat reduction efficiency as compared with traditional cylinder liners. The improved liner has an outer surface with a plurality of peaks and valleys. The peaks and valleys create an increased surface area of the outer surface thereby increasing contact with a cooling medium and more efficiently reducing heat within the engine.
U.S. Pat. No. 6,732,698, which issued to Bedwell et al. on May 11, 2004, describes an austempered gray iron cylinder liner and a method of manufacturing it. A cylinder liner for a high temperature, high performance engine is cast from gray iron material and thereafter austempered for a time sufficient to achieve a substantially bainitic microstructure that is stable against excessive thermal growth when the liner is exposed to extreme operating temperatures.
U.S. patent application Ser. No. 10/793,000 (M09720), which was filed by Wynveen et al. on Mar. 4, 2004, discloses an engine that is provided with a plurality of cylinders and cylinder liners that are shaped to define a plurality of spaces between the liners and the engine block. These spaces provide an insulative barrier that at least partially restricts the flow of heat from the liner into the engine block. This allows the liners to operate at elevated temperatures while avoiding a deleterious increase in the cooling water temperature as it flows through the passages within the engine block.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Those skilled in the art of engine design are familiar with many types of internal combustion engines that are cooled by providing a cooling fluid, such as water, which flows in thermal communication with heat producing portions of the engine. In automobile applications, the cooling system is a closed system in which a coolant is passed through a heat exchanger, such as an automobile radiator to remove heat from the coolant. The coolant is then recirculated through the engine cooling passages to remove heat from the engine. In certain marine propulsion systems, closed cooling systems are also used. However, in many types of marine propulsion systems, open cooling systems draw water from a body of water in which a marine vessel is operating and then circulate that water through the cooling passages of the engine. After heat has been removed by the water, the heated water is returned to the body of water from which it was originally drawn. Open cooling systems, such as those used in marine propulsion applications, have an inherent problem relating to the relative operating temperatures of various locations within the engine structure. If the temperatures within the cylinders of the engine are not sufficiently high, proper combustion is adversely affected and can result in the dilution of engine oil with liquid fuel in a manner that is known to those skilled in the art. The cooling channels of the engine, on the other hand, must be maintained at a temperature which is low enough to avoid separation of certain salts and minerals from the cooling water which was drawn from the body of water in which the marine vessel operates. If the cooling water passages reach a sufficiently high temperature, these salts and minerals can be deposited, or plated, on the walls of the cooling channels. This deposition of these minerals will adversely affect the thermal conductivity between the cooling channels and the engine block and can also lead to blockage of the cooling channels in some extreme cases. Therefore, in marine applications of open cooling systems, it would be significantly beneficial if the cooling water channels could be maintained at a temperature low enough to avoid the separation and deposition of minerals and salts on the walls of the cooling channels while also maintaining the cylinder temperatures at a sufficiently high magnitude to improve combustion and avoid oil dilution with liquid fuel.